Temperature control of piezo-electric crystal apparatus



March 12, 1935. M. osNos TEMPERATURE CONTROL OF PIEZO ELECTRIC CRYSTALAPPARATUS Filed Feb. 16, 1932 INVENTOR MENDEL OSNOS ATTORNEY PatentedMar. 12, 1935 TEMPERATURE CONTROL OF PIEZO-ELEC- TRIO CRYSTAL APPARATUSMendel Osnos, Berlin, Germany, assignor to Telefunken Gesellschaft fiirDrahtlose Telegraphie m. b. H-., Berlin, Germany, a corporation ofGermany Application February 16, 1932, Serial No. 593,253 In GermanyFebruary 19, 1931 7 Claims.

In radio work in general and in short wave WOI'kjlIl particular it isextremely important to stabilize the natural frequency of certaincircuits so. as, to insure the greatest possible constancy. What. is.used for this purpose are piezoelectric crystals. However, it has beenobserved that the natural period thereof varies with the temperature inthat it decreases with increase in temperature. According to the presentinvention the, harmful influence of temperature variations upon thenatural period of circuits containing piezo-electric crystals iscompensated wholly or partly by that in series or in parallel relationto. the crystals there. is connected a condenser whose capacitydecreases with increase of temperature. As a result automaticcompensation in whole or in part of the change in natural period of thecrystal is assured.

This invention will be more clearly understood by referring to theaccompanying drawing in which,

Fig. l is a; sectional view of a short wave piezoelectric crystalholder,

Fig. 2 is a circuit diagram wherein the capacity of a separate condenseris automatically varied with a temperature change in the piezo-electriccrystal apparatus, 7

Fig. 3 is a sectional view of a crystal holder similar to the holdershown in Fig. 1 except that the upper electrode serves as one electrodeor plate of a variable condenser, and there is also included in thisfigure the arrangement of a variable condenser plate or electrodepositioned above the combined crystal electrode and the condenser fixedplate. Also a partial circuit diagram is shown connected to the crystalholder which is similar to the circuit shown in Fig. 2.

Referring now to the drawing, Figure 1 illustrates one specificembodiment of this invention wherein the capacity of the apparatusvaries with change in temperature, and Figure 2 is a circuit diagramembodying another embodiment of the present invention wherein thecapacity of a condenser separate and apart from the crystal isautomatically varied with change in temperature of the apparatus.

Referring now in detail to Figure 1 of the drawing, 1 and 2 are metallicelectrodes of dissimilar polarity which are spaced apart from each otherby a cylindrical spacer means 3 possessing a suitable heat expansioncoefficient such as rubber, hard rubber (ebonit) or the like. Inasmuchas the heat expansion of the drum 3 is much higher than that of theinner cylinder 2 it will be seen that the distance between the twocapacitive surfaces of the electrodes grows with the temperature. Inother words, the capacity decreases incidentally, and this is adapted toalter wholly or in major part the harmful influence of the changes innatural frequency of the crystal occasioned by temperature fluctuationsby a convenient choice of the different parts of the con- 7 denser.

It will be understood that the construction of the variable condenser ashereinbefore disclosed is not the only possible form. Also a rotarycondenser could be employed whose angular displacement is controlled bythe intermediary of a suitable gearing by a body influenceable in itsdimensions by action of the temperature.

One scheme of using the arrangement here disclosed for the purpose ofinsuring automatic regulation of a thermionic tube is shown in Figure 2.Referring to the same, 5 is a cathode tube (thermionic valve) whose gridcircuit, as known in the prior art, contains a piezo-electric crystalstabilizer 6. '7 denotes a variable condenser according to the presentinvention connected in series with the crystal in any manner known tothe art and whose capacity changes automatically with the temperature. 8is an adjustable inductance coil which, in the presence of a definitetemperature, servesto wholly or partly compensate the capacitivereactance of the condenser I.

Figure 3 shows an embodiment of the crystal holder and a variablecondenser whose capacity decreases with rise in the temperature. Theplates or electrodes of the condenser are 1 and 14. 14 is adjustable byspindle 4 which has a screw thread. Spacer 13 to which 14 is securedconsists of a drum of hard rubber. The bottom condenser plate 1 alsoserves as the top electrode of crystal 6. 6 bears upon the lowerelectrode 2 of the crystal holder, which is built together withelectrode 1 by a suitable insulation cylinder 8. 9 is cement for 8 andelectrodes 1 and 2. 10, 11 and 12 are terminals. is electricallyconnected with spindle 4. If 10 and 12 are united with the externalcircuit then 6 is in series with the condenser. If 10 and 12 conjointlyare associated with one binding post of the outer circuit, and terminal11 with the other one, as shown in the drawing, then at least one of theelectrodes for the crystal 6 and the condenser variable plate areconnected in parallel.

I claim:

1. A piezo-electric crystal holder comprising two electrodes spacedapart from each other by insulation material, a piezo-electric crystalinterposed between the two electrodes, a condenser plate spaced byinsulation material and located above one of said electrodes andarranged for automatic temperature compensation wherein the spacebetween said condenser plate and at least one of the electrodes whichalso serves as the other plate of a condenser, is varied to change thecapacity between said electrode and said condenser plate correspondingwith a given change of temperature surrounding the crystal holder.

2. A piezo-electric crystal holder comprising two electrodes spacedapart from each other by insulation material, a piezo-electric crystalinterposed betwen the two electrodes, a condenser plate spaced byinsulation material and located above one of said electrodes andarranged for automatic temperature compensation wherein the spacebetween said condenser plate and at least one of the electrodes whichalso serves as the other plate of a condenser is varied to decrease thecapacity between said electrode and said condenser plate when thetemperature surrounding the crystal within the electrodes increases.

3. A piezo-electric crystal holder comprising two electrodes spacedapart from each other, a piezo-electric crystal interposed between thesaid electrodes, an insulating member spacing said electrodes, acondenser plate adjustably located directly above one of saidelectrodes, an insulating member supporting the condenserplate which isarranged for automatic temperature compensation by providing a variablespace between said condenser plate and the crystal electrode.

4. A piezo-electric crystal holder comprising a lower electrode having acentral cylindrical upright extending portion, an insulating casingslightly inside the periphery of the lower electrode,.

an upper electrode located directly above said insulating casing, apiezo-electric crystal interposed between the lower and upperelectrodes, an insulating member located above said upper electrode, ametallic cover having a threaded aperture located on top of saidinsulating member, a threaded spindle passing through said threadedaperture, a condenser plate secured to the end of said spindle andarranged for automatic temperature compensation by providing a spacewhich may be varied between said condenser plate and the upper crystalelectrode.

5. A piezo-electric crystal holder comprising a lower electrode having acentral cylindrical upright extending portion, a piezo-electric crystallocated on the top of the upright extending portion, an upper electrodelocated above said crystal and spaced from said lower electrode by aninsulating casing having alength substantially equal to the combinedlength of the upright extending portion of the lower electrode and thethickness of the piezo-electric crystal, an insulating member located ontop of said upper electrode and a metallic cover having an aperture forsecuring a spindle which supports one plate of a condenser, the otherplate of which is formed by one of said electrodes, said spindleinsuring automatic temperature compensation in which the space betweensaid condenser plate and the electrode serving as a condenser plate isvaried due to the different coeflicient of expansion of the supports forsaid condenser plate and said electrode.

6. A piezo-electric crystal holder comprising three electrodes spacedapart from each other by insulating material, a piezo-electric crystalinterposed between two of said electrodes, the third electrode beingsupported adjustably with respect to one of the other electrodes whichis located in a position which is intermediate one of the otherelectrodes to form the plate of a variable condenser, the'intermediatepositioned electrode also serving as the fixed plate of a variablecondenser.

'7. A piezc-electric crystal holder comprising three electrodes spacedapart from each other by insulating material, a piezo-electric crystalinterposed between two of said electrodes, the third electrode connectedin parallel relationship with at least one of the electrodes adjacentsaid crystal, said third electrode being supported adjustably withrespect to one of the other electrodes which is located in a positionwhich is intermediate one of the other electrodes to form the plate of avariable condenser, the intermediate positioned electrode also servingas the fixed plate of a variable condenser.

MENDEL OSNOS.

